Variable clinical spectrum of the most common inborn error of bile acid metabolism--3beta-hydroxy-Delta 5-C27-steroid dehydrogenase deficiency

EASL Clinical Practice Guidelines on genetic cholestatic liver diseases

Genetic cholestatic liver diseases are caused by (often rare) mutations in a multitude of different genes. While these diseases differ in pathobiology, clinical presentation and prognosis, they do have several commonalities due to their cholestatic nature. These Clinical Practice Guidelines (CPGs) offer a general approach to genetic testing and management of cholestatic pruritus, while exploring diagnostic and treatment approaches for a subset of genetic cholestatic liver diseases in depth. An expert panel appointed by the European Association for the Study of the Liver has created recommendations regarding diagnosis and treatment, based on the best evidence currently available in the fields of paediatric and adult hepatology, as well as genetics. The management of these diseases generally takes place in a tertiary referral centre, in order to provide up-to-date approaches and expertise. These CPGs are intended to support hepatologists (for paediatric and adult patients), residents and other healthcare professionals involved in the management of these patients with concrete recommendations based on currently available evidence or, if not available, on expert opinion.

Liver Disorders Caused by Inborn Errors of Metabolism

Inborn errors of metabolism (IEMs) are a vast array of inherited/congenital disorders, affecting a wide variety of metabolic pathways and/or biochemical processes inside the cells. Although IEMs are usually rare, they can be represented as serious health problems. During the neonatal period, these inherited defects can give rise to almost all key signs of liver malfunction, including jaundice, coagulopathy, hepato- and splenomegaly, ascites, etc. Since the liver is a vital organ with multiple synthetic, metabolic, and excretory functions, IEM-related hepatic dysfunction could seriously be considered life-threatening. In this context, the identification of those hepatic manifestations and their associated characteristics may promote the differential diagnosis of IEMs immediately after birth, making therapeutic strategies more successful in preventing the occurrence of subsequent events. Among all possible liver defects caused by IEMs, cholestatic jaundice, hepatosplenomegaly, and liver failure have been shown to be manifested more frequently. Therefore, the current study aims to review substantial IEMs that mostly result in the aforementioned hepatic disorders, relying on clinical principles, especially through the first years of life. In this article, a group of uncommon hepatic manifestations linked to IEMs is also discussed in brief.

Protocols of Investigation of Neonatal Cholestasis-A Critical Appraisal

Neonatal cholestasis (NC) starts during the first three months of life and comprises extrahepatic and intrahepatic groups of diseases, some of which have high morbimortality rates if not timely identified and treated. Prolonged jaundice, clay-colored or acholic stools, and choluria in an infant indicate the urgent need to investigate the presence of NC, and thenceforth the differential diagnosis of extra- and intrahepatic causes of NC. The differential diagnosis of NC is a laborious process demanding the accurate exclusion of a wide range of diseases, through the skillful use and interpretation of several diagnostic tests. A wise integration of clinical-laboratory, histopathological, molecular, and genetic evaluations is imperative, employing extensive knowledge about each evaluated disease as well as the pitfalls of each diagnostic test. Here, we review the difficulties involved in correctly diagnosing the cause of cholestasis in an affected infant.

Prognosis and clinical characteristics of patients with 3β-hydroxy-Δ5-C27-steroid dehydrogenase deficiency diagnosed in childhood: A systematic review of the literature

OBJECTIVES

3β-hydroxy-Δ5-C27-steroid dehydrogenase deficiency is a rare autosomal recessive condition. So far fewer than 100 cases have been reported and the factors affecting the prognosis are not yet established. The objective of this study is to explore a possible prediction of the outcome of this rare condition.

METHODS

This review was undertaken and reported in accordance with the preferred reporting items for systematic review and meta-analyses guidelines. Demographics, clinical features, gene data, treatment strategies and prognoses at the last follow-up were extracted and summarized. Patients were divided into 2 groups (alive with native liver and liver transplantation/died). Risk factors for the different clinical features were identified.

RESULTS

87 patients that were taken from 7 case reports and 9 case series were included. 38 (38/63, 63.0%) of them presented initial symptoms when they were younger than 1 month and 55 (55/63, 87.3%) less than 1 year. There is a larger proportion of patients younger than 1 month or 1 year at the age of symptom onset in the liver transplantation /died group than patients in alive with the native liver group. The majority of patients (53/62, 85.5%) were diagnosed before the age of 5 year. In all cases, 65 (predicted) pathogenic variants have been identified. Over 70% of patients carried an HSD3B7 variant on exon 1, 4, 5 or 6. 71 (81.6%) were alive at the last follow-up, 16 (18.4%) underwent liver transplantation or died. No significance was found between the group alive with native liver and group liver transplantation /died.

CONCLUSION

Age of onset of the symptoms may be a potential factor that determines the outcome of patients with 3β-HSD deficiency, patients presented with symptoms and signs at an age younger than 1 month or even 1 year may have a worse prognosis. Since there is no difference between clinical outcome and zygosity of gene mutation, we recommend a further study about any possible relationship between mutation site and clinical characteristics or prognosis.

Genetic spectrum and clinical characteristics of 3β-hydroxy-Δ5-C27-steroid oxidoreductase (HSD3B7) deficiency in China

BACKGROUND

Biallelic variants in HSD3B7 cause 3β-hydroxy-Δ5-C27-steroid oxidoreductase (HSD3B7) deficiency, a life-threatening but treatable liver disease. The goal of this study was to obtain detailed information on the correlation between the genotype and phenotype of HSD3B7 deficiency and to report on responses to primary bile acid therapy.

METHODS

The medical records of a cohort of 39 unrelated patients with genetically and biochemically confirmed HSD3B7 deficiency were examined to determine whether there exist genotype-phenotype relationships in this bile acid synthesis disorder.

RESULTS

In all, 34 of the 44 variants identified in HSD3B7 were novel. A total of 32 patients presented early with neonatal cholestasis, and 7 presented after 1-year of age with liver failure (n = 1), liver cirrhosis (n = 3), cholestasis (n = 1), renal cysts and abnormal liver biochemistries (n = 1), and coagulopathy from vitamin K1 deficiency and abnormal liver biochemistries (n = 1). Renal lesions, including renal cysts, renal stones, calcium deposition and renal enlargement were observed in 10 of 35 patients. Thirty-three patients were treated with oral chenodeoxycholic acid (CDCA) resulting in normalization of liver biochemistries in 24, while 2 showed a significant clinical improvement, and 7 underwent liver transplantation or died. Remarkably, renal lesions in 6 patients resolved after CDCA treatment, or liver transplantation. There were no significant correlations between genotype and clinical outcomes.

CONCLUSIONS

In what is the largest cohort of patients with HSD3B7 deficiency thus far studied, renal lesions were a notable clinical feature of HSD3B7 deficiency and these were resolved with suppression of atypical bile acids by oral CDCA administration.

The effectiveness of correcting abnormal metabolic profiles

Inborn errors of metabolism cause disease because of accumulation of a metabolite before the blocked step or deficiency of an essential metabolite downstream of the block. Treatments can be directed at reducing the levels of a toxic metabolite or correcting a metabolite deficiency. Many disorders have been treated successfully first in a single patient because we can measure the metabolites and adjust treatment to get them as close as possible to the normal range. Examples are drawn from Komrower's description of treatment of homocystinuria and the author's trials of treatment in bile acid synthesis disorders (3β-hydroxy-Δ⁵ -C₂₇ -steroid dehydrogenase deficiency and Δ⁴ -3-oxosteroid 5β-reductase deficiency), neurotransmitter amine disorders (aromatic L-amino acid decarboxylase [AADC] and tyrosine hydroxylase deficiencies), and vitamin B6 disorders (pyridox(am)ine phosphate oxidase deficiency and pyridoxine-dependent epilepsy [ALDH7A1 deficiency]). Sometimes follow-up shows there are milder and more severe forms of the disease and even variable clinical manifestations but by measuring the metabolites we can adjust the treatment to get the metabolites into the normal range. Biochemical measurements are not subject to placebo effects and will also show if the disorder is improving spontaneously. The hypothesis that can then be tested for clinical outcome is whether getting metabolite(s) into a target range leads to an improvement in an outcome parameter such as abnormal liver function tests, hypokinesia, epilepsy control etc. The metabolite-guided approach to treatment is an example of personalized medicine and is a better way of determining efficacy for disorders of variable severity than a randomized controlled clinical trial.

Use of dried urine spots for screening of inborn errors of bile acid synthesis

BACKGROUND

In pediatric patients with cholestasis of unknown cause, inborn errors of bile acid (BA) synthesis (IEBAS) may be considered. For the initial screening for IEBAS, clarification of the urine BA profile is essential. The transportation of urine in a frozen state via air delivery, however, is laborious and costly. This study assessed the feasibility of using dried urine spots (DUS) to establish a more convenient and affordable method of IEBAS screening.

METHODS

We created DUS using urine samples from patients with 3β-hydroxy-Δ5-C27-steroid dehydrogenase/isomerase deficiency (3β-HSD) and Δ4-3-oxo-steroid 5β-reductase deficiency as standard preparations. We started accepting DUS specimens by regular mail.

RESULTS

The ratio of unusual to usual BA is essential for the initial detection of IEBAS, and the recovery rates of abnormal BA were acceptable. The recovery rate of Δ4-BA on day 28 decreased to 31.8% at 25°C, and to 19.6% at 37°C. Therefore, the sending of DUS should be avoided under conditions of high temperature. Of a total of 49 children with cholestasis, eight new patients were diagnosed with IEBAS using this screening method.

CONCLUSION

The mailing screening system is expected to facilitate the shipment, from regions outside of Japan, of samples for IEBAS screening.

Cholic acid for primary bile acid synthesis defects: a life-saving therapy allowing a favorable outcome in adulthood

Background

Oral cholic acid (CA) replacement has been shown to be an effective therapy in children with primary bile acid synthesis defects, which are rare and severe genetic liver diseases. To date there has been no report of the effects of this therapy in children reaching adulthood. The aim of the study was to evaluate the long-term effectiveness and safety of CA therapy.

Methods

Fifteen patients with either 3β-hydroxy-Δ⁵-C₂₇-steroid oxidoreductase (3β-HSD) (n = 13) or Δ⁴–3-oxosteroid 5β-reductase (Δ⁴–3-oxo-R) (n = 2) deficiency confirmed by mass spectrometry and gene sequencing received oral CA and were followed prospectively.

Results

The median age at last follow-up and the median time of follow-up with treatment were 24.3 years (range: 15.3–37.2) and 21.4 years (range: 14.6–24.1), respectively. At last evaluation, physical examination findings and blood laboratory test results were normal in all patients. Liver sonograms were normal in most patients. Mean daily CA dose was 6.9 mg/kg of body weight. Mass spectrometry analysis of urine showed that excretion of the atypical metabolites remained low or traces in amount with CA therapy. Liver fibrosis scored in liver biopsies or assessed by elastography in 14 patients, after 10 to 24 years with CA therapy, showed a marked improvement with disappearance of cirrhosis (median score < F1; range: F0-F2). CA was well tolerated in all patients, including five women having 10 uneventful pregnancies during treatment.

Conclusions

Oral CA therapy is a safe and effective long-term treatment of 3β-HSD and Δ⁴–3-oxo-R deficiencies and allows affected children to reach adulthood in good health condition without the need for a liver transplantation.

Bile Acid Synthesis Disorders in Arabs: A 10-year Screening Study

OBJECTIVES

Early diagnosis of bile acid synthesis disorders (BASDs) is important because, untreated, these conditions can be fatal. Our objectives were to screen children with cholestasis or unexplained liver disease for BASD and in those with confirmed BASD to evaluate the effectiveness of cholic acid therapy.

METHODS

A routine serum total bile acid measurement was performed on children with cholestasis, liver cirrhosis, and liver failure. Patients were screened for BASD by fast atom bombardment ionization-mass spectrometry (FAB-MS) analysis of urine, and molecular analysis confirmed diagnosis. Treatment response to oral cholic acid (10-15 mg/kg bw/day) was assessed from liver function tests and fat-soluble vitamin levels. FAB-MS analysis of urine was used to monitor compliance and biochemical response.

RESULTS

Between 2007 and 2016, 626 patients were evaluated; 450 with infantile cholestasis. Fifteen cases of BASD were diagnosed: 12 presented with infantile cholestasis (2.7%, 7 boys), an 8-year-old boy presented with cirrhosis, and two 18-month-old boys presented with hepatomegaly and rickets. Eleven were caused by 3β-hydroxy-Δ-C27-steroid oxidoreductase dehydrogenase deficiency, 3 from Δ-3-oxosteroid 5β-reductase deficiency, and 1 had Zellweger spectrum disorder. In all but 1, serum total bile acids were normal or low. With cholic acid therapy, 10 are alive and healthy with their native liver. Liver failure developed in 3 infants despite therapy; 2 died and 1 underwent liver transplantation.

CONCLUSIONS

BASDs are rare but treatable causes of metabolic liver disease in Saudi Arabia. BASD should be considered in infants with cholestasis and low or normal serum total bile acid concentrations.

Atypical clinical presentation and successful treatment with oral cholic acid of a child with defective bile acid synthesis due to a novel mutation in the HSD3B7 gene

We report definitive diagnosis and effective treatment with oral cholic acid in one Italian male child affected by 3β-hydroxy-Δ⁵-C²⁷-steroid dehydrogenase (3β-HSD) deficiency. He presented with failure to thrive, hepatomegaly and multiple cystic images in kidneys; no biochemical evidence of cholestasis. Large amounts of bile acid metabolites was detected in urine by fast atom bombardment ionization mass spectrometry (FAB-MS). HSDH3B7 gene analysis identified one mutation in intron 4, at nucleotide 432, G>A substitution that has never been reported before.The replacement therapy with oral cholic acid started early after the diagnosis and is still ongoing. Three years later hepatomegaly is no longer evident, liver function is normal and the child is growing regularly. In our experience, clinical features of 3β-HSD deficiency can be very poor and even cholestasis can lack at diagnosis. Early replacement therapy with cholic acid is safe and leads to clinical and biochemical control of the disease.

Oral Cholic Acid Is Efficacious and Well Tolerated in Patients With Bile Acid Synthesis and Zellweger Spectrum Disorders

OBJECTIVES

Patients with bile acid synthesis disorders (BASDs) due to single enzyme defects (SEDs) or Zellweger spectrum disorders (ZSDs) accumulate hepatotoxic atypical bile acids resulting in potentially fatal progressive liver disease. We evaluated the efficacy and safety of oral cholic acid in patients with BASD.

METHODS

In this phase 3, open-label, single-arm, nonrandomized, noncomparative study conducted over 18 years, patients were administered cholic acid orally 10 to 15 mg · kg · day. The primary efficacy variables were changes from pre- to post-treatment in atypical urinary bile acids, liver chemistries (serum aspartate aminotransferase, alanine aminotransferase), and height and weight. Additional efficacy variables included changes in serum bilirubin and liver histology.

RESULTS

Of the 85 enrolled patients (63 with SED and 22 with ZSD), 79 received at least 1 dose of study medication; 70 patients (50 with SED and 20 with ZSD) were included in the modified intent-to-treat dataset. Cholic acid significantly improved urine bile acid metabolite scores (P < 0.0001) and serum aspartate aminotransferase and alanine aminotransferase (P < 0.0001) in patients with SED and ZSD. Cholic acid also improved height and weight percentiles in both groups, but only the change in weight was significant (P < 0.05). Serum direct bilirubin decreased significantly post-treatment (P < 0.001) in the intent-to-treat population, and liver biopsies showed either stable findings or histologic improvement in all parameters except bridging fibrosis. The overall safety profile of cholic acid was favorable, with no study drug-related serious adverse events or drug-related deaths reported.

CONCLUSIONS

Oral cholic acid is a safe, efficacious, and well-tolerated treatment for BASD due to SED and ZSD.

Attempt to Determine the Prevalence of Two Inborn Errors of Primary Bile Acid Synthesis: Results of a European Survey

OBJECTIVE

Inborn errors of primary bile acid (BA) synthesis are genetic cholestatic disorders leading to accumulation of atypical BA with deficiency of normal BA. Unless treated with primary BA, chronic liver disease usually progresses to cirrhosis and liver failure before adulthood. We sought to determine the prevalence of 2 common disorders, 3β-hydroxy-Δ-C27-steroid dehydrogenase (3β-HSD) and Δ-3-oxosteroid-5β-reductase (Δ-3-oxoR) deficiencies and to describe current diagnostic and treatment strategies among different European paediatric hepatology centres.

METHODS

A total of 52 clinical paediatric centres were approached and 39 centres in 21 countries agreed to participate in the Web-based survey. The survey comprised questions regarding general information, number of cases, diagnostic, and therapeutic management.

RESULTS

Seventeen centres located in 11 countries reported patients with inborn errors in primary BA synthesis, 22 centres never had cases diagnosed. In total, we could identify 63 patients; 55 with 3β-HSD and 8 with Δ-3-oxoR deficiency in 21 countries. The minimum estimated combined prevalence of these diseases was 1.13 cases per 10 million (0.99 and 0.14 for 3β-HSD and Δ-3-oxoR deficiencies, respectively). The surveyed colleagues indicated their main challenges to be the rarity of diseases and the lack of convenient laboratory facilities nearby.

CONCLUSION

We have identified the largest cohort of patients with 3β-HSD or Δ-3-oxoR deficiency described so far. These diseases are likely underdiagnosed mainly due to unawareness of their existence and the lack of laboratory facilities.

Child with Jaundice and Pruritus: How to Evaluate?

Jaundice with pruritus is a manifestation of cholestasis. The defective biliary drainage causes accumulation of substances that are usually excreted in bile, which in turn causes pruritus. The exact nature of the pruritogen is under evaluation. However, lysophosphatidic acid is the current favourite. The causes of cholestasis can be broadly classified as intra or extrahepatic, with intrahepatic disorders being more often associated with pruritus. Cholestatic phase of acute viral hepatitis, progressive familial intrahepatic cholestasis, syndromic and non-syndromic paucity of intralobular bile ductules, drug induced cholestasis and sclerosing cholangitis (SC) are the common causes in children. An algorithmic approach facilitates early etiological diagnosis by careful clinical evaluation combined with investigations including gamma glutamyl transpeptidase, radiological imaging (ultrasonography, magnetic resonance cholangiopancreatography), liver biopsy and genetic analysis. Management is largely supportive and includes nutritional rehabilitation with supplement of fat soluble vitamins and calcium, stepwise therapy of pruritus with drugs (ursodeoxycholic acid, rifampicin, bile acid sequestrants and/or opioid antagonists) and biliary diversion surgery. Complications of advanced liver disease and portal hypertension need to be addressed. Liver transplantation is required in children with refractory pruritus affecting the quality of life or those with end stage liver disease. Relief of biliary obstruction by endoscopy or surgery and treatment of diseases associated with SC like histiocytosis may be rewarding. Long-term follow-up for development of complications of liver disease and hepatocellular/ cholangiocarcinoma is essential. Thus, an early diagnosis and stepwise treatment with an understanding of the pathogenesis of pruritus in cholestatic disorders may decrease morbidity and mortality.

Metabolic Liver Disease: When to Suspect and How to Diagnose?

Metabolic liver diseases are still considered by many as a 'rare' diagnosis, though scenario has definitely changed in recent times. With recent advances and wider availablility of newer techniques, many of these are now amenable to diagnosis and optimum management. Though the logistics involved are still out of reach of a significant proportion of our population, a stepwise and methodological approach with simple diagnostic tests can help point towards a probable diagnosis (with resultant directed investigations), helping to avoid unnecessary and costly workup. This review focuses on diagnostic protocol-based approach to common metabolic liver diseases encountered frequently in pediatric hepatology.

Hypoglycemia due to 3β-Hydroxysteroid Dehydrogenase type II Deficiency in a Newborn

BACKGROUND

3β-hydroxysteroid dehydrogenase type II deficiency results in decreased production of all three groups of adrenal steroids. Recurrent hypoglycemia as a presenting feature of this disorder has not been reported earlier.

CASE CHARACTERISTICS

A genotypically and phenotypically normal female newborn delivered by in-vitro fertilization presenting with recurrent hypoglycemia. Primary adrenal insufficiency with insignificant mineralocorticoid deficiency and slightly elevated levels of 17-hydro-xyprogesterone, dehydroepian-drosterone sulphate and testosterone.

OUTCOME

Successfully managed only with corticosteroid replacement.

MESSAGE

Congenital adrenal hyperplasia can rarely cause recurrent hypoglycemia in newborns.

In-Depth Dissection of the P133R Mutation in Steroid 5β-Reductase (AKR1D1): A Molecular Basis of Bile Acid Deficiency

Human steroid-5β-reductase (aldo-keto reductase 1D1, AKR1D1) stereospecifically reduces Δ(4)-3-ketosteroids to 5β-dihydrosteroids and is essential for steroid hormone metabolism and bile acid biosynthesis. Genetic defects in AKR1D1 cause bile acid deficiency that leads to life threatening neonatal hepatitis and cholestasis. The disease-associated P133R mutation caused significant decreases in catalytic efficiency with both the representative steroid (cortisone) and the bile acid precursor (7α-hydroxycholest-4-en-3-one) substrates. Pro133 is a second shell residue to the steroid binding channel and is distal to both the cofactor binding site and the catalytic center. Strikingly, the P133R mutation caused over a 40-fold increase in Kd values for the NADP(H) cofactors and increased the rate of release of NADP(+) from the enzyme by 2 orders of magnitude when compared to the wild type enzyme. By contrast the effect of the mutation on Kd values for steroids were 10-fold or less. The reduced affinity for the cofactor suggests that the mutant exists largely in the less stable cofactor-free form in the cell. Using stopped-flow spectroscopy, a significant reduction in the rate of the chemical step was observed in multiple turnover reactions catalyzed by the P133R mutant, possibly due to the altered position of NADPH. Thus, impaired NADPH binding and hydride transfer is the molecular basis for bile acid deficiency in patients with the P133R mutation. Results revealed that optimal cofactor binding is vulnerable to distant structural perturbation, which may apply to other disease-associated mutations in AKR1D1, all of which occur at conserved residues and are unstable.

Liver biopsy in children: position paper of the ESPGHAN Hepatology Committee

Liver biopsy (LB) is still the criterion standard procedure for obtaining liver tissue for histopathological examination and a valuable tool in the diagnosis, prognosis, and management of many parenchymal liver diseases. The aim of this position paper is to summarise the present practice of paediatric LB and make recommendations about its performance. Although histological evaluation of the liver is important in assessing prognosis and exploring treatment, noninvasive techniques (ie, imaging, laboratory markers) may replace use of liver histology. The indications for LB are changing as present knowledge of aetiologies, pathomechanism, and therapeutic options in paediatric liver disease is evolving. Adult and paediatric literature was reviewed to assess the existing clinical practice of LB with focus on the technique, indications, risk of complications, and contraindications in paediatrics. This position paper presents types of LB, indications, complications, contraindications, and an essential checklist for paediatric LB.

Neonatal Cholestasis - Differential Diagnoses, Current Diagnostic Procedures, and Treatment

Cholestatic jaundice in early infancy is a complex diagnostic problem. Misdiagnosis of cholestasis as physiologic jaundice delays the identification of severe liver diseases. In the majority of infants, prolonged physiologic jaundice represent benign cases of breast milk jaundice, but few among them are masked and caused by neonatal cholestasis (NC) that requires a prompt diagnosis and treatment. Therefore, a prolonged neonatal jaundice, longer than 2 weeks after birth, must always be investigated because an early diagnosis is essential for appropriate management. To rapidly identify the cases with cholestatic jaundice, the conjugated bilirubin needs to be determined in any infant presenting with prolonged jaundice at 14 days of age with or without depigmented stool. Once NC is confirmed, a systematic approach is the key to reliably achieve the diagnosis in order to promptly initiate the specific, and in many cases, life-saving therapy. This strategy is most important to promptly identify and treat infants with biliary atresia, the most common cause of NC, as this requires a hepatoportoenterostomy as soon as possible. Here, we provide a detailed work-up approach including initial treatment recommendations and a clinically oriented overview of possible differential diagnoses in order to facilitate the early recognition and a timely diagnosis of cholestasis. This approach warrants a broad spectrum of diagnostic procedures and investigations including new methods that are described in this review.

Synthesis of atypical bile acids for use as investigative tools for the genetic defect of 3β-hydroxy-Δ(5)-C27-steroid oxidoreductase deficiency

Deficiency of 3β-hydroxy-Δ(5)-C27-steroid oxidoreductase (HSD3B7), an enzyme catalyzing the second step in the pathway for bile acid synthesis, leads to a complete lack of the primary bile acids, cholic and chenodeoxycholic acids, and the accumulation of 3β,7α-dihydroxy- and 3β,7α,12α-trihydroxy-Δ(5)-cholenoic acids. Patients affected by this autosomal recessive genetic defect develop cholestatic liver disease that is clinically responsive to primary bile acid therapy. Reference standards of these compounds are needed to facilitate diagnosis and to accurately quantify biochemical responses to therapy. Described are a novel synthesis of atypical bile acids that characterize the HSD3B7 deficiency and their effect on bile acid-activated nuclear receptors, target genes and cytochromes involved in bile acid homeostasis and detoxification. The failure of 3β-hydroxy-Δ(5)-cholenoic acids to function as FXR, PXR and CAR agonists and to exert hepatoprotective actions explains the mechanism for progressive cholestatic liver disease in patients with HSD3B7 deficiency.

Bile acid metabolism and signaling

Bile acids are important physiological agents for intestinal nutrient absorption and biliary secretion of lipids, toxic metabolites, and xenobiotics. Bile acids also are signaling molecules and metabolic regulators that activate nuclear receptors and G protein-coupled receptor (GPCR) signaling to regulate hepatic lipid, glucose, and energy homeostasis and maintain metabolic homeostasis. Conversion of cholesterol to bile acids is critical for maintaining cholesterol homeostasis and preventing accumulation of cholesterol, triglycerides, and toxic metabolites, and injury in the liver and other organs. Enterohepatic circulation of bile acids from the liver to intestine and back to the liver plays a central role in nutrient absorption and distribution, and metabolic regulation and homeostasis. This physiological process is regulated by a complex membrane transport system in the liver and intestine regulated by nuclear receptors. Toxic bile acids may cause inflammation, apoptosis, and cell death. On the other hand, bile acid-activated nuclear and GPCR signaling protects against inflammation in liver, intestine, and macrophages. Disorders in bile acid metabolism cause cholestatic liver diseases, dyslipidemia, fatty liver diseases, cardiovascular diseases, and diabetes. Bile acids, bile acid derivatives, and bile acid sequestrants are therapeutic agents for treating chronic liver diseases, obesity, and diabetes in humans.

Pediatric Cholestatic Disorders: Approach to Pathologic Diagnosis

This article addresses select liver diseases that are commonly seen in the pediatric group and pose diagnostic challenges in practice. The key genetic/molecular abnormalities, clinical features, histopathologic findings, diagnostic modalities, differential diagnoses, and possible pitfalls in diagnosis are discussed in detail. Although recent advances in understanding the pathophysiology of bile synthesis and transport along with advances in molecular genetics have allowed a better characterization of many of these liver diseases, significant overlap in the histopathologic features of many of these disorders still leads to diagnostic challenges for the pathologist.

Two neonatal cholestasis patients with mutations in the SRD5B1 (AKR1D1) gene: diagnosis and bile acid profiles during chenodeoxycholic acid treatment

BACKGROUND AND AIMS

In two Japanese infants with neonatal cholestasis, 3-oxo-Δ(4)-steroid 5β-reductase deficiency was diagnosed based on mutations of the SRD5B1 gene. Unusual bile acids such as elevated 3-oxo-Δ(4) bile acids were detected in their serum and urine by gas chromatography-mass spectrometry. We studied effects of oral chenodeoxycholic acid treatment.

PATIENTS AND METHODS

SRD5B1 gene analysis used peripheral lymphocyte genomic DNA. Diagnosis and treatment of these two patients were investigated retrospectively and prospectively investigated.

RESULTS

With respect to SRD5B1, one patient was heterozygous (R266Q, a novel mutation) while the other was a compound heterozygote (G223E/R261C). Chenodeoxycholic acid treatment was effective in improving liver function and decreasing unusual bile acids such as 7α-hydroxy- and 7α,12α-dihydroxy-3-oxo-4-cholen-24-oic acids in serum and urine.

CONCLUSION

Primary bile acid treatment using chenodeoxycholic acid was effective for these patients treated in early infancy before the late stage of chronic cholestatic liver dysfunction.

Homozygosity mapping identifies a bile acid biosynthetic defect in an adult with cirrhosis of unknown etiology

The most common inborn error of bile acid metabolism is 3β-hydroxy-Δ(5)-C(27)-steroid oxidoreductase (3β-HSD) deficiency, a disorder that usually presents in early childhood with hepatic dysfunction. Timely diagnosis of this disorder is crucial because it can be effectively treated with primary bile acid replacement. Here we describe a 24-year-old woman from Iran with cirrhosis of unknown etiology. Her sister and a first cousin died of cirrhosis (ages 19 and 6 years) and another 32-year-old first cousin had a self-limited liver disorder in childhood that resolved at age 9 years. The family history suggested that the affected family members were homozygous for a mutant allele inherited identical-by-descent. A genome-wide analysis of 2.4 million single nucleotide polymorphisms was performed to identify regions of homozygosity that were present in the proband and the 32-year-old first cousin, but not in a healthy relative. One of these regions contained the gene encoding 3β-HSD (HSD3B7). Sequence analysis of HSD3B7 revealed that the proband and her 32-year-old cousin were homozygous for a frameshift mutation (c.45_46del AG, p.T15Tfsx27) in exon 1. The diagnosis of 3β-HSD deficiency was confirmed by documenting high levels of 3β-hydroxy-Δ(5) bile acids in the serum of the proband and the 32-year-old first cousin using mass spectrometry. To our knowledge, the 32-year-old relative in this family represents the oldest asymptomatic patient with this disorder.

CONCLUSION

This study highlights the clinical utility of homozygosity mapping in diagnosing autosomal recessive metabolic disorders. This family illustrates the wide variation in expressivity that occurs in 3β-HSD deficiency and underscores the need to consider a bile acid synthetic defect as a possible cause of liver disease in adults.

Successful heterozygous living donor liver transplantation for an oxysterol 7α-hydroxylase deficiency in a Japanese patient

Only 2 patients with an oxysterol 7α-hydroxylase deficiency caused by mutations of the cytochrome P450 7B1 (CYP7B1) gene have been reported; for both, the outcome was fatal. We describe the clinical and laboratory features, the hepatic and renal histological findings, and the results of bile acid and CYP7B1 gene analyses for a third patient. This Japanese infant presented with progressive cholestatic liver disease and underwent successful heterozygous living donor liver transplantation. Sources of relevant data included medical records, hepatic and renal histopathological findings, gas chromatography/mass spectrometry analyses of bile acids in serum and urine samples, and analyses of the CYP7B1 gene in the DNA of peripheral blood lymphocytes. Large excesses of 3β-hydroxy-5-cholen-24-oic acid were detected in the patient's serum and urine. Cirrhosis and polycystic changes in the kidneys were documented. The demonstration of compound heterozygous mutations (R112X/R417C) of the CYP7B1 gene led to the diagnosis of an oxysterol 7α-hydroxylase deficiency. After liver transplantation with an allograft from a heterozygous living donor (the patient's mother), the features of decompensated hepatocellular failure abated, and the renal abnormalities were resolved. In conclusion, we report the first Japanese patient with an oxysterol 7α-hydroxylase deficiency associated with compound heterozygous mutations of the CYP7B1 gene; in this patient, liver transplantation with an allograft from a parental donor was effective.

Disorders of bile acid synthesis

Inborn errors of bile acid synthesis can produce life-threatening cholestatic liver disease (which usually presents in infancy) and progressive neurological disease presenting later in childhood or in adult life. Both types of disease can often be treated very effectively with bile acid replacement therapy and it is therefore important to diagnose these disorders as early as possible. The cholestatic disease in infancy is characterised by conjugated hyperbilirubinaemia with raised transaminases but normal γ-glutamyl transpeptidase and a biopsy showing a giant cell hepatitis. There is usually evidence of fat-soluble vitamin malabsorption. The neurological presentation often includes signs of upper motor neurone damage (spastic paraparesis). The most useful screening test for many of these disorders is analysis of urinary cholanoids (bile acids and bile alcohols); this is usually now achieved by electrospray ionisation tandem mass spectrometry. The disorders that are discussed in this review are: 3β-hydroxysteroid-Δ5-C27-steroid dehydrogenase deficiency, Δ4-3-oxosteroid 5β-reductase deficiency, sterol 27-hydroxylase deficiency (cerberotendinous xanthomatosis, CTX), oxysterol 7α-hydroxylase deficiency (including one form of hereditary spastic paraparesis) and the amidation defects, bile acid-CoA: aminoacid N-acyltransferase (BAAT) deficiency and bile acid-CoA ligase deficiency. The disorders of peroxisome biogenesis and peroxisomal β-oxidation that affect bile acid synthesis will be covered in the review by Ferdinandusse et al.

On the future of "omics": lipidomics

Following in the wake of the genomic and proteomic revolutions new fields of "omics" research are emerging. The metabolome provides the natural complement to the genome and proteome, however, the extreme physicochemical diversity of the metabolome leads to a subdivision of metabolites into compounds soluble in aqueous solutions or those soluble in organic solvents. A complete molecular and quantitative investigation of the latter when isolated from tissue, fluid or cells constitutes lipidomics. Like proteomics, lipidomics is a subject which is both technology driven and technology driving, with the primary technologies being mass spectrometry, with or without on-line chromatography and computer-assisted data analysis. In this paper we will examine the underlying fundamentals of different lipidomic experimental approaches including the "shotgun" and "top-down" global approaches, and the more targeted liquid chromatography - or gas chromatography - mass spectrometry approaches. Application of these approaches to the identification of in-born errors of metabolism will be discussed.

Molecular genetic and bile acid profiles in two Japanese patients with 3beta-hydroxy-DELTA5-C27-steroid dehydrogenase/isomerase deficiency

We report definitive diagnosis and effective chenodeoxycholic acid (CDCA) treatment of two Japanese children with 3[beta]-hydroxy-[DELTA]5-C27-steroid dehydrogenase/isomerase deficiency. Findings of cholestasis with normal serum [gamma]-glutamyltransferase activity and total bile acid concentration indicated the need for definitive bile acid analysis. Large amounts of 3[beta]-hydroxy-[DELTA]5 bile acids were detected by gas chromatography-mass spectrometry. HSD3B7 gene analysis using peripheral lymphocyte genomic DNA from the patients and their parents identified four novel mutations of the HSD3B7 gene in the patients. One had a homozygous mutation, 314delA; the other had compound heterozygous mutations: V132F, T149I, and 973_974insCCTGC. Interestingly, the second patient's mother had V132F and T149I mutations in one allele. Excessive 3[beta]-hydroxy-[DELTA]5-bile acids such as 3[beta],7[alpha]-dihydroxy- and 3[beta],7[alpha],12[alpha]-trihydroxy-5-cholenoic acids were detected in the first patient's urine; the second patient's urine contained large amounts of 3[beta]-hydroxy-5-cholenoic acid. Liver dysfunction in both patients decreased with ursodeoxycholic acid treatment, but unusual bile acids were still detected. Normalization of the patients' liver function and improvement of bile acid profiles occurred with CDCA treatment. Thus, we found mutations in the HSD3B7 gene accounting for autosomal recessive neonatal cholestasis caused by 3[beta]-hydroxy-[DELTA]5-C27-steroid dehydrogenase/isomerase deficiency. Early neonatal diagnosis permits initiation of CDCA treatment at this critical time, before the late cholestatic stage.